So I've been wondering for a while what a certian vacume hose was, and everyone I talked to wonered too. Well I think I figured it out. The vacume hose in question is the one that conects to the back of the top half of the stock intake, before the MAF. It runs from there to the top of the intake manifold. Well I think I final know waht it is. It is my belief that this mystery hose is what suplys air for the IAC. Does anyone know for sure? Am I right? Mystery solved?

It could be. I don't really know what it does. On another make of car there is a vacumn line that starts out from the airbox before the throttle (no MAF on this particular vehicle). Its purpose is to supply air to the EGR system. It has something to do with creating the vacumn, or possibly venting it.

My car is so far from stock I cannot verify the hook up you are referring to. My GUESS is its there to improve flow characteristics of the intake manifold. . . Huh? you say.

Fluid dynamics is extremely complex, but there may be a particular flow characteristic in the manifold that this vacuum line helps eliminate, possibly ensuring better flow distribution between runners. . . or who knows what, but I am sure its there to improve flow characteristics or prevents certain resonances at certain fluid flow velocities.

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